First time chick mom with a runt

We got 8 chicks Tuesday (Mar 3rd) that were hatched the day before. Unfortunately 2 passed :-( so now I am possibly over worried about losing another, especially because she (Isa Brown) is the smallest. She wasn't doing good the first day but I was dipping her beak to make sure she was drinking and she perked right up. Last night I was watching them and she was pecking at the food. All the others are doing great, almost full wing feathers working on tail feathers, and the little one is still working on wing feathers. They were weighed and she was 1.2 ounce and today down to 1.1 ounce. Should I be concerned? Anything more than electrolyte water and chick feed? Thanks for the advice!